Introduction: The purpose of this biomechanical study was to quantify the forces required for thumb opposition utilizing the four commonly used tendon transfers.

Methods: Five fresh-frozen cadaveric arms were used to quantify the forces required for thumb opposition from neutral to the index finger utilizing a portable Instron apparatus. The four tendon transfers performed were the: Flexor Digitorum Sublimis (FDS) or the Bunnell tranfer. Abductor Digiti Minimi (ADM) or the Huber transfer, the Extensor Indicis Proprius (EIP), and the Palmaris longus (PL) or the Camitz procedure. Force curves of thumb opposition were generated and work of flexion and stiffness quantified for each of the tendon transfers. Tendon transfers were compared within each arm allowing each arm to serve as its own control.

Results:

Extensor Indicis Proprius opponensplasty required the greatest amount of work to achieve the desired opposition in four of the five arms (P<0.005). In one of the five arms ADM/Huber transfer required the most work for opposition. (p<0.006). There were no differences in work of thumb opposition between the Palmaris and FDS transfers in all of the arms. Further, in four of the five arms the EIP opponensplasty had the greatest stiffness of all the tendon transfers. (p<0.0024).

Conclusion: Based on the results of this study we conclude that the EIP opponensplasty required the most work to achieve full opposition and required more force for each additional unit of motion at any point through the thumbs range of motion during opposition. The EIP opponesplasty should be used with caution in cases where extension force is not full.